Category Archives: Right Bundle Branch Block

The current study differs from any previous study in that we used supine rather than upright exercise. The physiologic response to exercise differs with the subject in the supine position where there is less of an increase in heart rate and more of an increase in blood pressure. Compared to upright exercise, there is an increase in venous return and a larger stroke volume, which should increase left ventricular wall tension. Despite the lower exercise heart rates achieved in this position, supine exercise has been shown to increase exercise-induced myocardial ischemia. Further studies are needed to determine whether our findings also apply to upright treadmill exercise.

Tanaka et al reported a retrospective study of 30 patients with right bundle branch block who had coronary angiography following a 12-lead ECG exercise treadmill test. All had symptoms suggestive of coronary artery disease and were predominantly male and middle-aged. Several had had a prior myocardial infarction. They found a sensitivity and specificity of 61 and 50 percent, respectively, using all 12 ECG leads. If leads Vj to V3 were excluded, the specificity was 100 percent, but the sensitivity fell to 44 percent. Although our patient population and methods differ from theirs, our results are similar. proventil inhaler

The current study is the first systematic investigation of the S-T segment response to exercise in individual leads of a standard 12-lead ECG in a large number of patients with right bundle branch block and suspected coronary artery disease. It demonstrates that the optimal interpretation of the exercise ECG in right bundle branch block includes the limb leads and V4 to V6 but not to V3. ampicillin antibiotic
One of the earliest attempts to study the S-T segment response to exercise in patients with right bundle branch block was that of Feil and Brofman in 1953. They found a very low sensitivity and specificity. However, their results are questionable, since coronary angiography was not available to establish or disprove the existence of coronary artery disease.

Lead V4 had a slightly lower sensitivity (29 percent), but an equal specificity (89 percent). The limb leads had a still lower sensitivity (24 percent), but a good specificity (86 percent). The right precordial leads (Vi to V3) had a clearly lower specificity of 56, 56 and 67 percent, respectively.

Forty-six of the 82 patients in this study had a radionuclide angiogram that was positive for ischemia. Thirty-one of these (67 percent) had a corresponding exercise ECG that was positive for ischemia in at least one of the 12 ECG leads. antibiotics levaquinSensitivity and Specificity of the 12-Lead Exercise ECG
As can be seen in Figure 1, the sensitivity was 48 percent for \yV6 and increased with the addition of the limb leads. However, there was a concomitant decrease in specificity. When all 12 ECG leads were included, the resultant sensitivity was 67 percent, but the specificity was only 39 percent. The best results (sensitivity = 59 percent, specificity = 80 percent) were obtained using leads V4, V5, V6 and the limb leads (Fig 1). The results were essentially identical if either criterion for an abnormal radionuclide angiogram (decrease in ejection fraction or new regional wall motion abnormality) was considered separately.

Coronary Angiography
Sixteen patients underwent coronary angiography within six months of the exercise radionuclide angiogram. Coronary angiography was performed using a standard percutaneous femoral or brachial cut-down approach. Multiple selective contrast injections were performed in the left and right coronary arteries. Caudal and cranial angulation were routinely employed. The degree of coronary artery stenosis was assessed visually in each of 23 different segments by two observers who usually were unaware of the radionuclide results. Significant coronary artery disease was established using the definitions of the Coronary Artery Surgery Study, ie, greater than or equal to 50 percent stenosis of the left main coronary artery and greater than or equal to 70 percent stenosis of the remaining coronary vessels were considered significant. canadian health and care mall

Exercise Electrocardiogram
The magnitude of S-T segment depression 80 ms after the J point was assessed visually in each of the 12 ECG leads and graded in the following categories: <1 mm, 1 mm, 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm. The configuration of the S-T segment was recorded as upsloping, horizontal or downsloping. Exercise ECG interpretation was done without knowledge of the results of the radionuclide angiogram. The exercise ECG was considered positive if there was at least 1.0 mV of horizontal or downsloping S-T-segment depression 80 ms after the ] point. In the presence of S-T-segment depression at rest, 1.0 mV of additional horizontal or downsloping S-T-segment depression was required. The individual leads in which positive S-T-segment changes occurred were recorded. buy cheap antibiotics

Exercise Protocol
The patients were exercised in the supine position. Three ECG leads were monitored continuously and a standard 12-lead ECG was performed every minute to monitor S-T segment changes. Blood pressure was measured in the right arm by cuff. Red blood cell labeling was performed with 30 mCi of technetium 99m using either the in vivo procedure or the modified in vivo procedure of Callahan et al. Acquisitions were gated to the R wave of the ECG and collected at 16 frames per cycle. After a radionuclide angiogram at rest, exercise was performed on a bicycle ergometer. The standard exercise protocol began at a work load of300 kg-m/min and increased every three minutes in increments of 300 kg-m/min. The exercise protocol was modified occasionally at the discretion of the monitoring physician. buy flovent inhaler

The value of the exercise ECG for the detection of coronary artery disease in patients with complete right bundle branch block has not been completely delineated. Standard textbooks make statements based on a small number of references that give meager data. Prior studies, which are scarce, have been hampered by small numbers,” the use of XYZ leads only or the inclusion of patients on digoxin and with prior myocardial infarction. No previous study has examined the incremental value of each ECG lead. This study was designed to use equilibrium radionuclide angiography to perform a detailed analysis of the supine exercise ECG for the detection of ischemia in patients with complete right bundle branch block.